Implementations of the claimed invention generally may relate to wireless communications, and in particular to beamforming in wireless communication networks.
In the downlink of closed-loop multiple input/multiple output (MIMO) beamforming in a wireless network comprising a subscriber station and a base station (BS), the subscriber station (also referred to at times herein as a mobile station (MS) or user equipment (UE)) quantizes the ideal beamforming matrix and sends a quantization index corresponding to the ideal beamforming matrix back to the base station (also referred to at times herein as a transmitter or enhanced node B (eNB)). The base station reconstructs the beamforming matrix according to the fed-back index and conducts the beamforming. Similarly, in the uplink, the base station quantizes the ideal beamforming matrix and the subscriber station reconstructs beamforming matrix according to the feedback. It is well known that beamforming increases the link performance and system throughput.
The beamforming matrix can be fed back differentially. The change between the current beamforming matrix and the previous one can be quantized by a codebook and the corresponding quantization index can be fed back. The quantization codebook determines the beamforming accuracy and tracking capability. The differential feedback can be applied across time and/or frequency.
Embodiments of the invention may find application in a wireless local area network (WLAN) or a wireless wide area network (WWAN) including a WiMAX (Worldwide Interoperability for Microwave Access) network or the like. WiMAX technology is based on the IEEE 802.16 family of standards, including IEEE 802.16e, IEEE 802.16m, and others. The invention herein may also be applicable to other WWANs such as those operating according to 3GPP Long Term Evolution (LTE) or LTE-Advanced, or similar, follow-on wireless standards. Further, while several specific standards have been set forth herein as examples of suitable applications, implementations herein are not limited to any particular standard or protocol.